Whereas AT&T expects to reap the benefits of its exclusive iPhone partnership, Verizon's FiOS business is growing rapidly. The firm added 303,000 new FiOS TV customers during the fourth quarter and 282,000 new FiOS Internet customers, a record for the company.

After an initial rally, shares of AT&T settled down 0.1% at $25.91 in Wednesday trading. Verizon's shares rose with the broader advance in stocks, closing up 96 cents, or 3.2%, to $30.92.